


No Coitus in the Bathroom

by SoloShikigami



Category: Undertale (Video Game)
Genre: BDSM, Bathroom Sex, M/M, Tentacle Sex
Language: English
Status: Completed
Published: 2019-11-24
Updated: 2019-11-24
Packaged: 2021-02-26 04:01:53
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,900
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21547267
Author URL: https://archiveofourown.org/users/SoloShikigami/pseuds/SoloShikigami
Summary: The sign above the bathroom said "Absolutely NO drug use and/or having coitus in the bathroom. May sound funny, but SERIOUSLY."Red was always one for pushing the rules and bringing Sans along for the ride.
Relationships: Kustard, Red/Sans, sans/sans
Comments: 8
Kudos: 144





	No Coitus in the Bathroom

**Author's Note:**

  * For [silverryu25](https://archiveofourown.org/users/silverryu25/gifts).



“Mph, I c-c-can’t believe you tal-taaahh-lked me I-in-into this!” Sans choked out in a horse whisper.

“Shush, pet, you want them to hear us?” Red asked, grinning against the side of Sans’ flushed, sweaty skull as he pumped his lover with three fingers.

Sans pressed his palm against his teeth as hard as he could as he squeezed his eyes shut. This was their second trip to the bathroom, Red was sitting on the toilet, Sans in his lap with his shorts around his ankles. The first time, Sans intended on simply washing his hands, not realizing that his lover had followed him. Red shoved him against the wall between the sinks when he was done, pressing against his back, pinning him against the cold tiles as he whispered all of the things he wanted to do to Sans, the way he wanted to ravage him, touch him, make him scream, and leave no doubt in anyone’s mind within a mile of them who he belonged to. As quickly as he was there, he was gone, leaving Sans breathless and wondering if that had just happened.

That encounter alone was enough to make Sans wet for the rest of the night, but Red decided to go a step further, running his foot along his femurs under the table despite the fact they shared that table with all of their alternates and brothers - but Sans was as into it as Red and damn it did the sharp-toothed bastard know it. With a quick, muttered apology, Sans excused himself from the table once they ordered and high-tailed it to the bathroom, Red on his heels, the story being that he was going to check on him.

Red knew just where to touch him, where to whisper, where to gently lick along his jaw and neck to drive him mad, and Sans was doing his best to keep it together until he was given permission to let it go.

“Red, close, so close,” Sans gasped quietly.

“Oh? Okay.”

Red pulled his hand away from Sans’ entrance, wiping some of the slick on his leg before abruptly standing, forcing Sans to trip into the wall of the bathroom stall.

“Don’t be too long, pet, and don’t you dare even think of getting off without my permission,” Red said, brushing a finger down his cheekbone before he left.

Sans could only stare as he tried to stop his legs from trembling as Red slipped out of the stall and he heard the door to the bathroom shut.

“What the hell?” Sans wondered, pulling up his shorts and going to wash his hands (again), before returning to the table.

“Are you all right, Brother?” Papyrus asked, looking at Sans with concern as he came back to the table.

“Oh, sure, bro, I’m good,” Sans said with his usual grin.

The conversation between the others continued and Sans did his best to catch up, though his mind was distracted with trying to figure out what Red’s game was this time. Red was smiling at him from his spot across from the table as if nothing happened, even tipping his bottle of mustard towards the slightly smaller skeleton before squeezing some onto his tongue.

Sans did not miss the fact that Red deliberately swirled his tongue with a little more panache and enthusiasm than was required, given the situation.

A buzz from his pocket made him jump and he nearly scrambled to take out his phone.

_Wishin’ this tongue was swirlin’ inside of ya, pet._

Red.

Sans couldn’t help a small frown as his fingers moved to reply,

_After that tease you’ll be lucky if I let you lick the cum off my leg after I make you watch me jerk off._

Sans gave a small smirk and discreetly slipped the phone back into his pocket. He watched Red as he casually slipped his hand into the pocket of his black jacket and pulled out his own phone. There was a flicker across his eyes; they glanced sharply at Sans as he tensed, but it all lasted less than a moment before Red tapped on the phone and shoved it back where it came from.

_Baby doll, do you really want to test this?_

As Sans began to tap out a reply, another buzzing sensation made him stop. It wasn’t his phone. He waited for a second, and as the buzzing had come and gone, he returned to his task. He didn’t even begin his retort when the buzzing returned, lasting a second longer before disappearing. It was coming from his pelvic area. He glanced down to his shorts, then back up at Red, who was laughing at some comment Stretch had made. Sans returned to his phone, but now lost his train of thought, and just as he was beginning to get it back on track, the buzzing returned at a higher intensity, and it made his phone slip from his hands.

“Sans! I told you no phones at the table at gatherings!” Papyrus scolded him.

Sans could barely chance glancing up at his brother, though it was apparent no one could hear the buzzing that was shaking the lower half of his body. He looked over at Red, who was looking at him with some question and concern, though there was a nasty glint in his eye that told Sans that he did something. Sans noted Red’s hand never left the pocket his phone was in.

“S-sorry, Pap,” he murmured.

The vibration stopped, the conversation continued, but now Sans was at a loss. He slowly reached out to pick up his phone, and nearly dropped it when it went off again. As he tapped it open, the vibration started again with a lower intensity, but just as distracting.

_Enjoying the new wireless bullet toy, pet? I figured some public discipline might improve your attitude._

Sans looked up. Red was now staring at him, a small movement in his pocket and the vibration intensified a little.

_I slipped it in during your last trip to the bathroom. You really are such a slut, so wet with the prospect of me fucking you in a bathroom that you didn’t notice? Shame on you, pet._

The vibration intensified again, and Sans had to grip his phone tight to keep from dropping it again. He was borderline panting when Red dialed it back down.

_If it’s too much, you may ask me permission to use the bathroom and remove it. In the meantime, be a good boy and put your phone away like your brother asked, and your Master orders._

Sans shuddered, nodding slightly, and moving slowly to put his phone into his pocket. The vibration started again, low, and Sans did his best to keep from moaning, still hearing Red’s order in his head.

* ~ * ~ * ~ * ~ *

Sans didn’t know how much longer he could hang on. He was lucky that he normally did keep fairly quiet during gatherings, unless it was to get involved in a pun war with Red and Stretch, otherwise it would have risen suspicions.

“Hey, Sansy, you okay?” Blue asked.

Or not… out of all of the skeletons, Blue was the most observant, and he was sitting in a position where he could see Sans fully.

“Yeah, yeah, just… lunch never settled I guess,” Sans said with as reassuring of a grin as he could muster.

“If you weren’t up for coming out you should have said something!” Papyrus said worriedly.

“Nah, nah, Pap, I’m fine,” Sans said, waving him off and trying to not make any indications that the vibrations on his pelvis got more intense. “I’m sure once the food gets here, it’ll help, I might also be really, really hungry.”

Sans glanced over at Red, who only gave him a neutral glance back. He was starting to panic a little because the others were also looking at Sans with concern, and while that was disturbing for him under normal circumstances, this was just unbearable.

“Oh, hey, here comes the grub,” Red said.

Thankfully he wasn’t just saying it as a distraction, three servers approached their table, each carrying a large tray and began setting their food down. Red used the moment to turn the bullet up again while everyone was looking at their dishes, thanking the servers, and taking out their phones to take pictures of their plates. Sans made a small choking sound which went unnoticed as he gripped the edge of the table.

“Hey, do you need the bathroom again?” Red asked.

Sans nodded.

“You can go if you like,” he said, taking a sip of his drink.

Sans nearly teleported to the bathroom.

“Red, do you know what is going on with Sans?” Papyrus asked, looking exasperated that his brother was missing from the table yet again.

“Yeah, kinda,” Red gave Papyrus a sheepish sort of smile. “I’ve been giving him a hard time, teasing ‘im an’ such. Lemme go talk to ‘im.”

Red was giving the impression that he was poking fun at Sans and perhaps going too far with his own jokes and puns - which most everyone knew to be a touch on the inappropriate side (in fact, when he and Sans had first met it was what made Sans keep his distance in the beginning), so no one really knew or thought to question it.

Well, almost no one.

“They’re fucking in the bathroom, aren’t they?” Blue murmured to his brother.

“Yep,” the other murmured in return. “Let them have their fun.”

* ~ * ~ * ~ * ~ *

“Red, please, please, I can’t take anymore,” Sans begged the moment Red came into the bathroom, nearly falling to his knees as he grabbed the other by the jacket.

“Aww, my poor baby,” Red purred, wrapping an arm around Sans’ back to pull him back up. “Come on, I’ll cure all of your ills, but first.”

He pulled Sans in and kissed him deeply. Normally Sans would have pushed him away, uncomfortable with such intimate displays in public, but he was so frustrated and turned on, he didn’t care.

“Such a needy little brat,” Red said, running his thumb along ((the bottom)) the underside of his jaw.

“You’re the brat,” Sans muttered, a flash of defiance in his eyes.

“Oh, ho, I see,” Red slipped a hand into his pocket and turned the vibrator up to its max.

Sans gasped and his legs nearly gave out, but Red was there to steady him with a somewhat evil chuckle and without another word, pushed Sans towards the large stall.

“W-wait, wh-what are y-you-?” Sans asked.

“You talk way too much darling.”

Sans went to ask, but then something slippery slipped into his mouth. He started and looked up at Red with wide eyes. Red settled himself on the toilet, crossing one leg over his knee and leaning back. A few slithery red tentacles were waving out from his body, a pair heading towards Sans.

“Relax, babe, let Daddy take care of ya,” Red snickered.

Sans looked ready to protest, but the tentacles grabbed his wrists and ankles while other began to undress him. Other tentacles moved to caress him over his sensitive spots, luring him into a more receptive, relaxed state.

“Very good, Sansy,” Red murmured. “Go ahead, suck on the one in yer mouth, bet ya c’n make that one feel real good.”

He fingered the controller in his pocket to lighten up on the vibrator, and Sans communicated his appreciation by beginning to suck on the tentacle in his mouth, forming his tongue to wrap around it, sucking on it as best his could.

“Mmm, good job, sweetheart,” Red said, his hips shifting a little. “I think that deserves a little something something.”

Red made his tentacles slip around his floating ribs and lower spine, two of Sans’ more sensitive spot. He moaned appreciatively.

“Shh, don’t wanna get caught now,” Red said softly.

Red summoned a few more tentacles and used them to lift Sans up off the ground and pinning him to the wall. Sans let out a small but muffled cry of surprise.

“Won’t do any good if someone comes in and sees two sets of feet,” Red explained, turning the vibrator up slightly again.

Sans visibly shuddered, but sucked on the tentacle in his mouth with a quiet moan.

Red grinned, continuing to caress Sans, his tentacles moving across his spine and around his pelvis. Judging by the way his magic was beginning to form, Sans seemed to be enjoying himself, and Red was getting turned on as well.

“Come on, sweetheart, give me something to play with besides my own dick,” Red urged, one hand slipping into his own pants to rub himself.

It didn’t take long for Sans to form a cock of his own, and Red hummed in appreciation. He made his tentacles move to bring Sans closer to him.

“Since yer makin’ me miss my dinner, might as well feast on you,” Red smirked, taking Sans’ cock into his mouth with ease, gripping onto his legs and having one of his own tentacles jerk him off as he feasted on Sans.

Sans was trying to hide his moan, and even with the thick tentacle in his mouth, it was still escaping. Red hummed around Sans, his sharp teeth scraping along Sans’ shaft, making him squirm.

“Mmmmm, yeah, that’s it, baby,” Red said, pumping Sans with one hand while he spoke. “So sweet and sexy fer me, y’drive me wild, sweetheart, I wanna fuck you so badly.”

Sans looked down at him with a whimper, his eyes turning into hazy heart shapes and nodding.

“Oh, darling,” Red moaned, standing up, pulling the tentacle out of Sans’ mouth to kiss him, one hand reaching under him to seek out his entrance.

Sans began to shake, between the vibrator still inside his pelvis, Red kissing him, and now his fingers exploring his entrance was really bringing him close already. He let out a small cry when Red’s fingers brushed near the vibrator, making the feeling more intense.

“Ooo, I felt that,” Red chuckled, his hand shoving down his pants. “Yer already getting’ all wet fer me, yer magic just achin’ t’have me take ya, huh?”

“Please, Red,” Sans begged.

Red sat back on the toilet, bringing Sans with him, pulling him in for another deep kiss as he pulled him into his lap, entering him with a groan. Sans gasped, panting, dropping his head onto Red’s shoulder. His arms were being held behind his back, his legs were wrapped by the tentacles too, but he felt safe, and Red’s sharp teeth against his neck reminded him that he was loved.

“I love you, Sans,” Red murmured, vocalizing his feelings.

“Mmph, please, Red, I love you, too, just…” Sans moaned.

“Heh, a bit too much fer ya?”

“Why you basta-ah!”

Red moved Sans up then pulled him down hard. One tentacle returned, wrapping around Sans to gag him as Red impaled him over and over.

“Yeah, I’m a bastard,” Red chuckled. “But I’m also the bastard that’s gonna make y’cum in less than five minutes, cause’s yer that tight, that keyed up, and jus’ that much of a slut for my cock, ain’tcha?”

Sans’ breath was coming out in huffs, his eyes squeezed shut, his moans muffled behind the thick tentacle. Red was right as he felt the telltale flutters from his lover’s body.

“Tha’s it sweetheart, cum all over me, I’m gonna fill ya up good,” Red pressed.

Red brought a hand to stroke Sans’ neglected cock, his thumb running over the head as he pumped him, and as he predicted, Sans came only a few moments later. His back arched, a muffled scream was music to Red’s ears, and the tightness around him drew his own orgasm out, Sans’ magic spilling over his hand.

Sans’ tensed body suddenly relaxed and he slumped slightly, still being held mostly by Red’s tentacles. Part o him admired how careful his lover was, his soul warmed by the other being sure to take care of him. Soft kisses over his face, and one on his mouth surprised him and made him realize the gagging tentacle was gone.

“Such a good boy,” Red said, turning the vibrator off and gently pulling out of Sans. “Hang on fer a sec, let me get that toy outta ya, then… well, hell, this is a mess to clean up.”

Sans leaned his head against Red’s shoulder, still breathing heavily, trying to not moan in pleasure and hoped he really wasn’t getting off at Red’s fingers moving inside of him to find the vibrator.

“I am so gonna kick your ass later for this,” Sans swore.

“Oh? Then mebbe I’ll jus’ leave that in there fer collateral,” Red said with a smirk. “An y’can clean yerself up.”

Sans couldn’t stop the pleased shiver than ran down his spine and the way he almost instinctively wrapped his arms around Red.

“I’ll be good,” he promised in a quiet voice.

Red chuckled, his fingers finally finding the toy, and gently pulling it out, noticing the quiet but pleased whimper from Sans, and he kissed him.

“Glad to hear it, sweetheart.”

* ~ * ~ * ~ * ~ *

Meanwhile at the table, Blue had Sans and Red’s dinners packed into doggy bags.

“WHAT ARE THEY DOING?!” Edge growled crossly.

“Should I go check on them?” Papyrus asked for at least the tenth time.

“No!” Swap and Blue nearly shouted.

**Author's Note:**

> Like what you read? Please check out my social media for more fun!  
> [ My Tumblr](https://soloshikigami.tumblr.com/)  
> [ My Twitter](https://twitter.com/SoloShikigami)


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